991637556100 has 27 divisors (see below), whose sum is σ = 2151875106031. Its totient is φ = 396651039200.

The previous prime is 991637556053. The next prime is 991637556131. The reversal of 991637556100 is 1655736199.

The square root of 991637556100 is 995810.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 69207929476 + 922429626624 = 263074^2 + 960432^2 .

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 8 ways as a sum of consecutive naturals, for example, 9908310 + ... + 10007890.

Almost surely, 2^991637556100 is an apocalyptic number.

991637556100 is the 995810-th square number.

It is an amenable number.

991637556100 is an abundant number, since it is smaller than the sum of its proper divisors (1160237549931).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

991637556100 is an frugal number, since it uses more digits than its factorization.

991637556100 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 199176 (or 99588 counting only the distinct ones).

The product of its (nonzero) digits is 1530900, while the sum is 52.

The spelling of 991637556100 in words is "nine hundred ninety-one billion, six hundred thirty-seven million, five hundred fifty-six thousand, one hundred".